Method of operating and controlling electric motors.



No. 765,209. PATENTED JULY 19, 1904.

v w. STORER. METHOD OF OPERATING AND GONTROLLING ELECTRIC MOTORS.

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NITED STATES Patented July 19, 1904.

PATENT Orricn.

NORMAN WV. STORER, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A COR- PORATION OF PENNSYLVANIA.

' METHOD OF OPERATING AND CONTROLLING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent N 0. 765,209, dated July19, 1904.

Application filed August 15, 1902. Serial No. 119,764. (No model.)

To It Ill/7,0777 it nuty concern:

Be it known thatI, NORMAN SToRER, a citizen of the United States, and aresident of Pittsburg, in the. county of Allegheny and 1 ries-woundmotors of the direct-current type.

I by decreasing the ampere-hour capaclty and lowering the voltage ofdischarge, but it in ;jures,the plates of the battery, and therefore Theobject of my invention is to provide a method of motor operation andcontrol which shall insure a maximum torque with a relatively smallconsumption of current and gradual speed variation with a minimumexpenditure of energy.

My invention is primarily designed for utilization in the operation ofmotors from secondary batteries to drive vehicles, and it will beincreases the cost of maintenance.

. My invention provides tor keeping the maximum discharge rate of thebattery relatively low by so designing the motor that the field- .magnetis worked far below the saturation- ;point under all normalfloads.

were entirely unsaturated throughout the maximum range of load, thetorquewould} increase asthe square of the current, while if thefieldwere saturated.throughout the entire range of load the torque would.in-;

crease .in direct proportion to'the current.

Therefore, in the one-case. in order toobtain four times fulleloadtorque it would be neces' sary to have twice full-load current, while inthe other case it would be necessary to have four times full-loadcurrent. Both of these cases are extreme. The motor which I propose touse is .not absolutely unsaturated and requires about 2.3 timesfull-load current to give four times full-load torque, while theordinary motorwhich is worked near saturation at full load will requirefrom three to three and onehalf times full-load current to give fourtimes full-load torque. The difference between these figures will make avery material difference in the ampere-hour capacity and the mileage ofa battery when run over a given route.

In order to secure the greatest advantage from under saturation of thefield magnetic circuit, I have designed a motor to be operated with thefield-coils all in series at the first notch and with the two halves inmultiple on the second notch of the controller. This motor, inconnection with the control system which applies only half-voltage tothe motor on the first two notches and full voltage on the last twonotches, gives a perfect system of speed control with the leastexpenditure of energy and the smallest maximum discharge rate for thebattery. If we consider the normal torque to be that obtained when thecoils are connected two halves in multiple, we can obtain this torquewith the field-coils connected .all in series (thus giving double theturns in the fielch) and with the field magnetic circuit unsaturated byan expenditure of current of about .7 of the normal current; but as themotor is not absolutely unsaturated it requires about .75 of thefull-load current to give the full-load torque when the coils are all inseries. .It must be rememberedthat the speed will be decreased in,proportion as the current is decreased, .so

.thati'or the. full-load torque: the current requiredwith thefield-coilsall in series will be only .75 of the normal current, and thespeed will be approximately .75 of the normal speed.

It will thus beseen that with the control system which .I. employ,inwhich. the start is made on the. first notch with no resistance in edin parallel relation to each other.

circuit but with the battery connected to give .5 voltage and with thefield-coils all in series, a speed will be obtained which will besomewhat less than .25 of the normal speed of the vehicle. On the secondnotch, with the fields connected two halves in parallel and with thebattery connected to give half-voltage, the speedwill be approximately.5 of the normal. On the third notch, with the full battery voltage andwith the motor-field coils connected all in series, the motor will runat approximately .75 of the normal speed, and on the last notch, withthe full battery voltage operating and with the fields connected two.halves in parallel, the motor will operateat its normal speed.

on the first notch, insure a smooth acceleration from notch to notch,provide four eflicient running speeds," and keep the discharge rate ofthe battery down to a minimum. With this systemof control it isimpossible for the driver to discharge the battery at such an abnormalrate as with the ordinary method of control, which operates with asaturated-field motor and has only two running-notches.

5 is a similar diagram of circuit connections for maximum speed.

In the drawings the armature-winding 1 of the motor is at all times inseries with its fieldmagnet winding, the latter being, however,

'so divided and arranged with reference to the controller that portionsof it may be connect- I have shown the field-magnet winding ascomprising four coils 2, 3, 4, and 5 so combined with a controller 6that they may all be connected in series or so that coils 2 and 3 may becon-- neeted in series with each other and as a set connected inparallel with coils 4 and 5, which are also in series with each other.For the purposes of my invention, as will be understood from theoperation hereinafter described, the motor should be sodesigned that themagnetic circuits for the windings 2, 3,

4, and 5 shall be worked well below saturation. The source of energy fordriving the motor is represented by a secondary battery '7, the cells ofwhich are divided into two vided into a greater number of groups ofcells, 5 so as to prov1de a greater number of voltages,

I have thus provided a method of control which .will always start thevehicle.

and the field-magnet windings of the motor might also be divided into agreater number of sections, so as to give greater variation of fieldstrength, if desired. It is to be understood, therefore, that theinvention is not limited as regards the number and variations of eitherfield-magnet-Winding sections or battery groups, and consequently it isnot limited to any specific number of applied voltages or fieldstrengths.

In the controller shown the fingers l0 and 11 are respectively connectedto the terminals of the armature l, the fingers 12 and 13 to theterminals of the field-magnet coil 5, the fingers 14 and 15 to theterminals of the fieldmagnet coil 4, the fingers 16 and 17 to theterminals of the field-magnet coil 3, the fingers 18 and 19 to theterminals of the fieldmagnet coil 2, the fingers 20 and 21 to theterminals of the group of cells 8, and the fingers 22 and 23 .to theterminals of the group of cells 9.

It will be seen that when the drum 24 of the controller, Which is shownas developed into a plane in Fig. 1, is rotated to bring the first setof contact-pieces into engagement with the corresponding fingers thegroups of cells 8 and 9 will be connected in parallel relation and thefield-magnet coils 2, 3, 4, and 5 will be connected in series with eachother and with the armature 1, as indicated in Fig. 2, so-thatsubstantially one-half the normal battery voltage will be supplied tothe motor, and on account of the series relation of the field-magnetcoils there Will be a maximum number of ampere-turns and a correspondingfield strength, and the motor will run at a minimum speed and with amaximum torque.

When the drum is moved another step to bring the second line ofcontact-pieces into engagement with the fingers, the groups of cells 8and 9 will remain, as before, connected in parallel; but coils2 and 3,constituting one half of the field-magnet winding, will be connected inparallel with the other half of the winding represented by coils 4 and5, thus reducing the ampere-turns, and consequently the field strength,and therefore at the same 'voltage as before, giving an increased motorspeed. Movement of the drum another step to bring the third line ofcontact-pieces into engagement with the fingers will serve to connectall of the battery-cells in series and also the field-magnet coils inseries, thus providing the full battery voltage with maximum fieldstrength for the motor, this arrangement being such as to give a stillfurther increase of motor speed. Further movement of the drum to bringthe fourth line of contact-pieces into engagement with the fingersserves to connect the battery-cells is series, as before, and one halfof the field-magnet winding represented by the coils 2 and 3 in parallelwith the other half of the winding represented by coils 4 and 5, thusproviding full battery volnations and manipulations shown, though forthe operation of vehicle-motors by means of secondary batteries thenumber of speed variations shown will generally be found Sufiicient, andthe provision of means for securing a greater number of speeds wouldproduce such complications of controlling apparatus as would be likelyto more than ofl'set any advantage that might be gained by the greaterspeed variations.

I claim as my invention- 1. The method of operating a series-woundelectric motor, having an unsaturated-field magnetic circuit, at varyingspeeds, which consists in supplying substantially one half voltage withthe motor-field-magnet coils in series for minimum speed and maximumtorque, connecting substantially one half of the field-magnet winding inparallel with the other half Without change of voltage for the next hiher speed, supplying full voltage with the fieldcoils in series for thenext higher speed and.

connecting the two halves of the field-magnet winding without change ofvoltage for maximum speed.

2. The method of operating a series-wound electric motor, having anunsaturated-field magnetic circuit, from a secondary battery at varyingspeeds, which consists in connecting one half the battery-cells inparallel relation with the other half to the motor-field magnet windingin series, second, connecting one half the battery-cells in parallelrelation with the other half to the two halves of the field-magnetWinding in parallel, third, connecting the battery-cells in series witheach other to the entire field-magnet Winding in series, and, fourth,connecting the battery-cells inseries with each other to the two halvesof the fieldmagnet winding in parallel.

3. The method of effecting speed acceleration of an electric motor,having an unsatu-- rated-field magnetic circuit, without undueexpenditure of energy, which consists in first supplying such energyfrom a secondary battery having its cells connected in parallel to themotor-field magnet and armature coils in series, then connecting onehalf of the fieldmagnet coils in parallel with the other half, and thenchanging both the battery-cells and the field-magnet coils to seriesrelation.

4. The method of operating an electric motor, having anunsaturated-field magnet, at different speeds by energy from a secondarybattery without undue expenditure of such energy, which consists inconnecting one half the battery-cells in parallel relation with theother half and the twohalves of the motorfield-magnet windingsuccessively in series and in parallel relation for two successivespeeds and connecting the battery-cells in series and the two halves ofthe field-magnet winding successively in series and in parallel relationfor two successive higher speeds.

5. The method of operating a series-wound electric motor, having anunsaturated-field magnet, at different speeds and with a minimumexpenditure of energy, which consists in varying the electromotive forceapplied to the motor terminals and at the same time varying the fieldampere-turns without adding or subtracting any magnetizing-winding.

6. The method of operating a series-wound electric motor, having anunsaturated-field magnetic circuit, at different speeds, which consistsin applying a given electromotive force to the motor terminals with thefieldmagnet winding connected in series, then changing two substantiallyequal portions of said winding to parallel relation and then increasingthe applied electromotive force.

7. The method of varying the speed of a series-wound electric motorhaving an unsaturated-field magnetic circuit, which consists in firstsupplying a minimum voltage with the field-magnetwindings connected formaximum field strength, then changing the connections of said winding toreduce the field strength,

then increasing both the applied voltage and the field strength andfinally reducing the field strength without changing the appliedvoltage, all without adding or subtracting any magnetizing-winding.

8. The method of varying the speed of a series-wound electric motorhaving an unsaturated-field magnetic circuit, which consists insupplying a given voltage and varying the field ampere-turns of themotor without adding or subtracting any magnetizing-winding and thenchanging the voltage and varying the field ampere-turns under the newvoltage in a similar manner.

In testimony whereof I have hereunto subscribed my name this 9th day ofAugust, 1902.

NORMAN WV. STORER. WVitnesses:

GEo-V. MILLIGAN, J. 0. Mouse.

